The invention relates to a printing drum for use in electrostatic photocopying methods. From the state of the art it is known to utilize printing drums for electrostatic photocopy methods. These printing drums have a surface layer consisting of light-sensitive, chargeable material such as selenium or chalcogenide glasses (arsenic-selenium alloys and compounds). It is also known to utilize organic photoconductors therefor, for example, PVK.
The printing drums mentioned are used to photograph an image of the pattern to be copied, which is projected onto the surface of the drum after a charge resulting from a corona discharge. This image is an electrostatic charge image, which by using a toner powder, subsequently is formed on a printing drum coated with printing ink. The actual printing process is is carried out by means of letting paper and a surface of the printing drum run one atop the other.
The following requirements result for devices of this known copying method. The material of the surface layer of the printing drum must have a high light sensitivity, and indeed in the spectral range of technologically conventional light sources. The material must have a specific electric impedance in darkness of magnitude .rho..gtoreq.10.sup.12 ohm.multidot.cm. The material must also exhibit properties which remain unaltered with a continuous load, i.e. which operate in a fatigue-proof manner and which is sufficiently resistant to abrasion for the copying.